Microsoft, among the world's most valuable companies by market capitalization, was founded in 1975 by Bill Gates and Paul Allen.
The two childhood friends created Microsoft after seeing the Altair 8800, an early personal computer kit, featured on the cover of Popular Electronics. They developed a version of the BASIC programming language for the machine and formed a company originally called Micro-Soft.
Microsoft’s early business focused on software rather than building complete computers. Its agreement to provide an operating system for IBM’s personal computer, released in 1981, helped make MS-DOS a standard in the rapidly growing PC industry.
Steve Ballmer joined Microsoft in 1980 and later became chief executive, but he was not a founder. Paul Allen left day-to-day operations in 1983 after receiving a Hodgkin lymphoma diagnosis, while remaining a major shareholder and technology philanthropist.